WSDL (Web Services Description Language) is a web-services description language that describes web-services by specifying parts, messages, operations, ports, port types and services. It comprises an XML (extensible Markup Language) vocabulary that standardizes how organizations describe web-services. A WSDL document includes various elements, which define and describe the web-services offered by the author, for example a service provider.
BizTalk Messaging Framework is a messaging framework that provides specifications for the design and development of messaging solutions for communication between applications and organizations. This specification builds upon standard and emerging Internet technologies, such as Hypertext Transfer Protocol (HTTP), Multipurpose Internet Mail Extensions (MIME), XML, and Simple Object Access Protocol (SOAP), The BizTalk Messaging Framework specifies the format of a web-services message. It defines various SOAP header elements, such as a “process” element and a “message” element.
Service requestors can access web-services remotely across the Internet using SOAP. Using WSDL, a service provider can inform service requestors on how to request information from the service provider. Service providers use WSDL to describe how their services can be used and to describe how the messages are to be built. Once the service requestor has access to the WSDL interface for a specific web-service, it uses SOAP messages to communicate with the service provider. Those messages may include SOAP header elements. The interaction between the service provider and the service requestor is achieved through message exchange. However, in some cases, defining what messages may be exchanged between the service provider and the service requestor may not be enough. For example, WSDL does not allow the service provider to specify the manner in which messages may be secured.